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Practice Exam Questions - Exam 4 Patho

Terms in this set (46)

A. Uncal
Uncal herniation causes compression of the third cranial nerve and the posterior cerebral artery. Thus the symptoms presented in this case are present. Tonsillar herniation evolves very rapidly and can result in death in a matter of minutes. Signs usually include precipitous changes in blood pressure and heart rate, small pupils, disturbances in conjugate gaze, ataxic breathing, and problems swallowing. Subfalcine herniation occurs when a lesion in one hemisphere is large enough to cause a lateral shift across the midline of the intracranial cavity, forcing the neurologic gyrus under the falx cerebri. This results in distortion and compression of the internal cerebral vein. Subfalcine herniation can be asymptomatic and generally carries a better prognosis than other types of brain herniation. The greatest danger results from compression of blood vessels, particularly the ipsilateral anterior cerebral artery, which can cause further cerebral ischemia and edema and contribute to the ICP elevation. Transtentorial herniation can occur rapidly or slowly, depending on the type of lesion. The speed with which the process is recognized is a critical factor in patient survival. Slowly dilating or odd-shaped pupils is an ominous sign that indicates compression of the third cranial nerve and midbrain. Transtentorial herniations are associated with significant intracranial hypertension and may initiate vascular compression and CSF obstruction, which then contribute to the existing problem of ischemia and hypertension.